Merge "Turn on LTO for libc++.so" am: 0860713e9e am: 8be550233c

Original change: https://android-review.googlesource.com/c/platform/external/libcxx/+/2623791

Change-Id: I3bb5b83ed0ad7b5fba2a90771e51f4611accc29a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>